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fetchmail !!!fetchmail NAME SYNOPSIS YOUR FRIENDLY DEBIAN MAINTAINER WARNS DESCRIPTION GENERAL OPERATION USER AUTHENTICATION AND ENCRYPTION DAEMON MODE ADMINISTRATIVE OPTIONS RETRIEVAL FAILURE MODES SPAM FILTERING SMTP/ESMTP ERROR HANDLING THE RUN CONTROL FILE INTERACTION WITH RFC 822 CONFIGURATION EXAMPLES THE USE AND ABUSE OF MULTIDROP MAILBOXES EXIT CODES FILES ENVIRONMENT SIGNALS BUGS AND KNOWN PROBLEMS AUTHOR SEE ALSO APPLICABLE STANDARDS ---- !!NAME fetchmail - fetch mail from a POP, IMAP, ETRN, or ODMR-capable server !!SYNOPSIS __fetchmail__ [[''option...''] [[''mailserver...'']__ fetchmailconf__ !!YOUR FRIENDLY DEBIAN MAINTAINER WARNS fetchmailconf has a blacklist of known-troublesome servers. Use it. Also, you must remember that fetchmail ''will'' discard mail if your MTA returns error codes 552 or 553, or any of the ''antispam'' error codes. The only way to avoid that is the ''keep'' fetchmail option. By default, codes 571, 550, 501 and 554 are in the ''antispam'' list. You have been warned. !!DESCRIPTION ''fetchmail'' is a mail-retrieval and forwarding utility; it fetches mail from remote mailservers and forwards it to your local (client) machine's delivery system. You can then handle the retrieved mail using normal mail user agents such as mutt(1), elm(1) or ''Mail''(1). The ''fetchmail'' utility can be run in a daemon mode to repeatedly poll one or more systems at a specified interval. The ''fetchmail'' program can gather mail from servers supporting any of the common mail-retrieval protocols: POP2, POP3, IMAP2bis, IMAP4, and IMAPrev1. It can also use the ESMTP ETRN extension and ODMR. (The RFCs describing all these protocols are listed at the end of this manual page.) While ''fetchmail'' is primarily intended to be used over on-demand TCP/IP links (such as SLIP or PPP connections), it may also be useful as a message transfer agent for sites which refuse for security reasons to permit (sender-initiated) SMTP transactions with sendmail. As each message is retrieved ''fetchmail'' normally delivers it via SMTP to port 25 on the machine it is running on (localhost), just as though it were being passed in over a normal TCP/IP link. The mail will then be delivered locally via your system's MDA (Mail Delivery Agent, usually sendmail(8) but your system may use a different one such as ''smail'', ''mmdf'', ''exim'', or ''qmail''). All the delivery-control mechanisms (such as ''.forward'' files) normally available through your system MDA and local delivery agents will therefore work. If no port 25 listener is available, you must configure Debian fetchmail explicitly to use an MDA. If the program ''fetchmailconf'' is available, it will assist you in setting up and editing a fetchmailrc configuration. It runs under X and requires that the language Python and the Tk toolkit be present on your system. If you are first setting up fetchmail for single-user mode, it is recommended that you use Novice mode. Expert mode provides complete control of fetchmail configuration, including the multidrop features. In either case, the `Autoprobe' button will tell you the most capable protocol a given mailserver supports, and warn you of potential problems with that server. !!GENERAL OPERATION The behavior of ''fetchmail'' is controlled by command-line options and a run control file, ''~/.fetchmailrc'', the syntax of which we describe in a later section (this file is what the ''fetchmailconf'' program edits). Command-line options override ''~/.fetchmailrc'' declarations. Each server name that you specify following the options on the command line will be queried. If you don't specify any servers on the command line, each `poll' entry in your ''~/.fetchmailrc'' file will be queried. To facilitate the use of ''fetchmail'' in scripts and pipelines, it returns an appropriate exit code upon termination -- see EXIT CODES below. The following options modify the behavior of ''fetchmail''. It is seldom necessary to specify any of these once you have a working ''.fetchmailrc'' file set up. Almost all options have a corresponding keyword which can be used to declare them in a ''fetchmailrc'' file. Some special options are not covered here, but are documented instead in sections on AUTHENTICATION and DAEMON MODE which follow. __General Options__ __-V, --version__ Displays the version information for your copy of ''fetchmail.'' No mail fetch is performed. Instead, for each server specified, all the option information that would be computed if ''fetchmail'' were connecting to that server is displayed. Any non-printables in passwords or other string names are shown as backslashed C-like escape sequences. This option is useful for verifying that your options are set the way you want them. __-c, --check__ Return a status code to indicate whether there is mail waiting, without actually fetching or deleting mail (see EXIT CODES below). This option turns off daemon mode (in which it would be useless). It doesn't play well with queries to multiple sites, and doesn't work with ETRN or ODMR. It will return a false positive if you leave read but undeleted mail in your server mailbox and your fetch protocol can't tell kept messages from new ones. This means it will work with IMAP, not work with POP2, and may occasionally flake out under POP3. __-s, --silent__ Silent mode. Suppresses all progress/status messages that are normally echoed to standard error during a fetch (but does not suppress actual error messages). The --verbose option overrides this. __-v, --verbose__ Verbose mode. All control messages passed between ''fetchmail'' and the mailserver are echoed to stdout. Overrides --silent. Doubling this option (-v -v) causes extra diagnostic information to be printed. __Disposal Options__ __-a, --all__ (Keyword: fetchall) Retrieve both old (seen) and new messages from the mailserver. The default is to fetch only messages the server has not marked seen. Under POP3, this option also forces the use of RETR rather than TOP. Note that POP2 retrieval behaves as though --all is always on (see RETRIEVAL FAILURE MODES below) and this option does not work with ETRN or ODMR. __-k, --keep__ (Keyword: keep) Keep retrieved messages on the remote mailserver. Normally, messages are deleted from the folder on the mailserver after they have been retrieved. Specifying the __keep__ option causes retrieved messages to remain in your folder on the mailserver. This option does not work with ETRN or ODMR. __-K, --nokeep__ (Keyword: nokeep) Delete retrieved messages from the remote mailserver. This option forces retrieved mail to be deleted. It may be useful if you have specified a default of __keep__ in your ''.fetchmailrc''. This option is forced on with ETRN and ODMR. __-F, --flush__ POP3/IMAP only. Delete old (previously retrieved) messages from the mailserver before retrieving new messages. This option does not work with ETRN or ODMR. Warning: if your local MTA hangs and fetchmail is aborted, the next time you run fetchmail, it will delete mail that was never delivered to you. What you probably want is the default setting: if you don't specify `-k', then fetchmail will automatically delete messages after successful delivery. __Protocol and Query Options__ __-p, --protocol __ (Keyword: proto[[col]) Specify the protocol to use when communicating with the remote mailserver. If no protocol is specified, the default is AUTO. ''proto'' may be one of the following: AUTO Tries IMAP, POP3, and POP2 (skipping any of these for which support has not been compiled in). POP2 Post Office Protocol 2 POP3 Post Office Protocol 3 APOP Use POP3 with old-fashioned MD5-challenge authentication. RPOP Use POP3 with RPOP authentication. KPOP Use POP3 with Kerberos V4 authentication on port 1109. SDPS Use POP3 with Demon Internet's SDPS extensions. IMAP IMAP2bis, IMAP4, or IMAP4rev1 (''fetchmail'' autodetects their capabilities). ETRN Use the ESMTP ETRN option. ODMR Use the the On-Demand Mail Relay ESMTP profile. All these alternatives work in basically the same way (communicating with standard server daemons to fetch mail already delivered to a mailbox on the server) except ETRN and ODMR. The ETRN mode allows you to ask a compliant ESMTP server (such as BSD sendmail at release 8.8.0 or higher) to immediately open a sender-SMTP connection to your client machine and begin forwarding any items addressed to your client machine in the server's queue of undelivered mail. The ODMR mode requires an ODMR-capable server and works similarly to ETRN, except that it does not require the client machine to have a static DNS. __-U, --uidl__ (Keyword: uidl) Force UIDL use (effective only with POP3). Force client-side tracking of `newness' of messages (UIDL stands for ``unique ID listing'' and is described in RFC1725). Use with `keep' to use a mailbox as a baby news drop for a group of users. __-P, --port __ (Keyword: port) The port option permits you to specify a TCP/IP port to connect on. This option will seldom be necessary as all the supported protocols have well-established default port numbers. __--principal __ (Keyword: principal) The principal option permits you to specify a service principal for mutual authentication. This is applicable to POP3 or IMAP with Kerberos authentication. __-t, --timeout __ (Keyword: timeout) The timeout option allows you to set a server-nonresponse timeout in seconds. If a mailserver does not send a greeting message or respond to commands for the given number of seconds, ''fetchmail'' will hang up on it. Without such a timeout ''fetchmail'' might hang up indefinitely trying to fetch mail from a down host. This would be particularly annoying for a ''fetchmail'' running in background. There is a default timeout which fetchmail -V will report. If a given connection receives too many timeouts in succession, fetchmail will consider it wedged and stop retrying, the calkling user will be notified by email if this happens. __--plugin __ (Keyword: plugin) The plugin option allows you to use an external program to establish the TCP connection. This is useful if you want to use socks, SSL, ssh, or need some special firewalling setup. The program will be looked up in $PATH and can optionally be passed the hostname and port as arguments using __--plugout __ (Keyword: plugout) Identical to the plugin option above, but this one is used for the SMTP connections (which will probably not need it, so it has been separated from plugin). __-r __ (Keyword: folder[[s]) Causes a specified non-default mail folder on the mailserver (or comma-separated list of folders) to be retrieved. The syntax of the folder name is server-dependent. This option is not available under POP3, ETRN, or ODMR. __--tracepolls__ (Keyword: tracepolls) Tell fetchail to poll trace information in the form `polling %s account %s' to the Received line it generates, where the %s parts are replaced by the user's remote name and the poll label (the Received header also normally includes the server's truename). This can be used to facilate mail filtering based on the account it is being received from. __--ssl__ (Keyword: ssl) Causes the connection to the mail server to be encrypted via SSL. Connect to the server using the specified base protocol over a connection secured by SSL. SSL support must be present at the server. If no port is specified, the connection is attempted to the well known port of the SSL version of the base protocol. This is generally a different port than the port used by the base protocol. For IMAP, this is port 143 for the clear protocol and port 993 for the SSL secured protocol. __--sslcert __ (Keyword: sslcert) Specifies the file name of the client side public SSL certificate. Some SSL encrypted servers may require client side keys and certificates for authentication. In most cases, this is optional. This specifies the location of the public key certificate to be presented to the server at the time the SSL session is established. It is not required (but may be provided) if the server does not require it. Some servers may require it, some servers may request it but not require it, and some servers may not request it at all. It may be the same file as the private key (combined key and certificate file) but this is not recommended. __--sslkey __ (Keyword: sslkey) Specifies the file name of the client side private SSL key. Some SSL encrypted servers may require client side keys and certificates for authentication. In most cases, this is optional. This specifies the location of the private key used to sign transactions with the server at the time the SSL session is established. It is not required (but may be provided) if the server does not require it. Some servers may require it, some servers may request it but not require it, and some servers may not request it at all. It may be the same file as the public key (combined key and certificate file) but this is not recommended. If a password is required to unlock the key, it will be prompted for at the time just prior to establishing the session to the server. This can cause some complications in daemon mode. __--sslproto __ (Keyword: sslproto) Forces an ssl protocol. Possible values are `__ssl2__', `__ssl3__' and `__tls1__'. Try this if the default handshake does not work for your server. __--sslcertck__ (Keyword: sslcertck) Causes fetchmail to strictly check the server certificate against a set of local trusted certificates (see the __sslcertpath__ option). If the server certificate is not signed by one of the trusted ones (directly or indirectly), the SSL connection will fail. This checking should prevent man-in-the-middle attacks against the SSL connection. Note that CRLs are seemingly not currently supported by OpenSSL in certificate verification! Your system clock should be reasonably accurate when using this option! __--sslcertpath __ (Keyword: sslcertpath) Sets the directory fetchmail uses to look up local certificates. The default is your OpenSSL default one. The directory must be hashed as OpenSSL expects it - every time you add or modify a certificate in the directory, you need to use the __c_rehash__ tool (which comes with OpenSSL in the tools/ subdirectory). __--sslfingerprint__ (Keyword: sslfingerprint) Specify the fingerprint of the server key (an MD5 hash of the key) in hexadecimal notation with colons separating groups of two digits. The letter hex digits must be in upper case. This is the default format OpenSSL uses, and the one fetchmail uses to report the fingerprint when an SSL connection is established. When this is specified, fetchmail will compare the server key fingerprint with the given one, and the connection will fail if they do not match. This can be used to prevent man-in-the-middle attacks. __Delivery Control Options__ __-S __ (Keyword: smtp[[host]) Specify a hunt list of hosts to forward mail to (one or more hostnames, comma-separated). Hosts are tried in list order; the first one that is up becomes the forwarding target for the current run. Normally, `localhost' is added to the end of the list as an invisible default. However, when using Kerberos authentication, the FQDN of the machine running fetchmail is added to the end of the list as an invisible default. Each hostname may have a port number following the host name. The port number is separated from the host name by a slash; the default port is 25 (or ``smtp'' under IPv6). If you specify an absolute pathname (beginning with a /), it will be interpreted as the name of a UNIX socket accepting LMTP connections (such as is supported by the Cyrus IMAP daemon) Example: --smtphost server1,server2/2525,server3,/var/imap/socket/lmtp This option can be used with ODMR, and will make fetchmail a relay between the ODMR server and SMTP or LMTP receiver. __--fetchdomains __ (Keyword: fetchdomains) In ETRN or ODMR mode, this option specifies the list of domains the server should ship mail for once the connection is turned around. The default is the FQDN of the machine running fetchmail. __-D __ (Keyword: smtpaddress) Specify the domain to be appended to addresses in RCPT TO lines shipped to SMTP. The name of the SMTP server (as specified by --smtphost, or defaulted to __--smtpname __ (Keyword: smtpname) Specify the domain and user to be put in RCPT TO lines shipped to SMTP. The default user is the current local user. __-Z __ (Keyword: antispam) Specifies the list of numeric SMTP errors that are to be interpreted as a spam-block response from the listener. A value of -1 disables this option. For the command-line option, the list values should be comma-separated. __-m __ (Keyword: mda) You can force mail to be passed to an MDA directly (rather than forwarded to port 25) with the -mda or -m option. To avoid losing mail, use this option only with MDAs like procmail or sendmail that return a nonzero status on disk-full and other resource-exhaustion errors; the nonzero status tells fetchmail that delivery failed and prevents the message from being deleted off the server. If ''fetchmail'' is running as root, it sets its userid to that of the target user while delivering mail through an MDA. Some possible MDAs are ''not'' use an MDA invocation like '' __--lmtp__ (Keyword: lmtp) Cause delivery via LMTP (Local Mail Transfer Protocol). A service port ''must'' be explicitly specified (with a slash suffix) on each host in the smtphost hunt list if this option is selected; the default port 25 will (in accordance with RFC 2033) not be accepted. __--bsmtp __ (keyword: bsmtp) Append fetched mail to a BSMTP file. This simply contains the SMTP commands that would normally be generated by fetchmail when passing mail to an SMTP listener daemon. An argument of `-' causes the mail to be written to standard output. Note that fetchmail's reconstruction of MAIL FROM and RCPT TO lines is not guaranteed correct; the caveats discussed under THE USE AND ABUSE OF MULTIDROP MAILBOXES below apply. __Resource Limit Control Options__ __-l __ (Keyword: limit) Takes a maximum octet size argument. Messages larger than this size will not be fetched and will be left on the server (in foreground sessions, the progress messages will note that they are __-w __ (Keyword: warnings) Takes an interval in seconds. When you call ''fetchmail'' with a `limit' option in daemon mode, this controls the interval at which warnings about oversized messages are mailed to the calling user (or the user specified by the `postmaster' option). One such notification is always mailed at the end of the the first poll that the oversized message is detected. Thereafter, renotification is suppressed until after the warning interval elapses (it will take place at the end of the first following poll). __-b __ (Keyword: batchlimit) Specify the maximum number of messages that will be shipped to an SMTP listener before the connection is deliberately torn down and rebuilt (defaults to 0, meaning no limit). An explicit --batchlimit of 0 overrides any limits set in your run control file. While sendmail(8) normally initiates delivery of a message immediately after receiving the message terminator, some SMTP listeners are not so prompt. MTAs like qmail(8) and smail(8) may wait till the delivery socket is shut down to deliver. This may produce annoying delays when ''fetchmail'' is processing very large batches. Setting the batch limit to some nonzero size will prevent these delays. This option does not work with ETRN or ODMR. __-B __ (Keyword: fetchlimit) Limit the number of messages accepted from a given server in a single poll. By default there is no limit. An explicit --fetchlimit of 0 overrides any limits set in your run control file. This option does not work with ETRN or ODMR. __-e __ (keyword: expunge) Arrange for deletions to be made final after a given number of messages. Under POP2 or POP3, fetchmail cannot make deletions final without sending QUIT and ending the session -- with this option on, fetchmail will break a long mail retrieval session into multiple subsessions, sending QUIT after each sub-session. This is a good defense against line drops on POP3 servers that do not do the equivalent of a QUIT on hangup. Under IMAP, ''fetchmail'' normally issues an EXPUNGE command after each deletion in order to force the deletion to be done immediately. This is safest when your connection to the server is flaky and expensive, as it avoids resending duplicate mail after a line hit. However, on large mailboxes the overhead of re-indexing after every message can slam the server pretty hard, so if your connection is reliable it is good to do expunges less frequently. Also note that some servers enforce a delay of a few seconds after each quit, so fetchmail may not be able to get back in immediately after an expunge -- you may see ''fetchmail'' to only issue expunges on every Nth delete. An argument of zero suppresses expunges entirely (so no expunges at all will be done until the end of run). This option does not work with ETRN or ODMR. __Authentication Options__ __-u __ (Keyword: user[[name]) Specifies the user identification to be used when logging in to the mailserver. The appropriate user identification is both server and user-dependent. The default is your login name on the client machine that is running ''fetchmail.'' See USER AUTHENTICATION below for a complete description. __-I __ (Keyword: interface) Require that a specific interface device be up and have a specific local or remote IP address (or range) before polling. Frequently ''fetchmail'' is used over a transient point-to-point TCP/IP link established directly to a mailserver via SLIP or PPP. That is a relatively secure channel. But when other TCP/IP routes to the mailserver exist (e.g. when the link is connected to an alternate ISP), your username and password may be vulnerable to snooping (especially when daemon mode automatically polls for mail, shipping a clear password over the net at predictable intervals). The --interface option may be used to prevent this. When the specified link is not up or is not connected to a matching IP address, polling will be skipped. The format is: interface/iii.iii.iii.iii/mmm.mmm.mmm.mmm The field before the first slash is the interface name (i.e. sl0, ppp0 etc.). The field before the second slash is the acceptable IP address. The field after the second slash is a mask which specifies a range of IP addresses to accept. If no mask is present 255.255.255.255 is assumed (i.e. an exact match). This option is currently only supported under Linux and FreeBSD. Please see the __monitor__ section for below for FreeBSD specific information. __-M __ (Keyword: monitor) Daemon mode can cause transient links which are automatically taken down after a period of inactivity (e.g. PPP links) to remain up indefinitely. This option identifies a system TCP/IP interface to be monitored for activity. After each poll interval, if the link is up but no other activity has occurred on the link, then the poll will be skipped. However, when fetchmail is woken up by a signal, the monitor check is skipped and the poll goes through unconditionally. This option is currently only supported under Linux and FreeBSD. For the __monitor__ and __interface__ options to work for non root users under FreeBSD, the fetchmail binary must be installed SGID kmem. This would be a security hole, but fetchmail runs with the effective GID set to that of the kmem group ''only'' when interface data is being collected. __--auth __ (Keyword: auth[[enticate]) This option permits you to specify an authentication type (see USER AUTHENTICATION below for details). The possible values are __any__, `__password__', `__kerberos_v5__' and `__kerberos__' (or, for excruciating exactness, `__kerberos_v4__'), gssapi, ''cram-md5'', ''otp'', ''ntlm'', and __ssh__. When __any__ (the default) is specified, fetchmail tries first methods that don't require a password (GSSAPI, KERBEROS_IV); then it looks for methods that mask your password (CRAM-MD5, X-OTP, NTLM); and only if the server doesn't support any of those will it ship your password en clair. Other values may be used to force various authentication methods (__ssh__ suppresses authentication). Any value other than ''password'', ''cram-md5'', ''ntlm'' or ''otp'' suppresses fetchmail's normal inquiry for a password. Specify ''ssh'' when you are using an end-to-end secure connection such as an ssh tunnel; specify gssapi or __kerberos_v4__ if you are using a protocol variant that employs GSSAPI or K4. Choosing KPOP protocol automatically selects Kerberos authentication. This option does not work with ETRN. __Miscellaneous Options__ __-f __ Specify a non-default name for the ''~/.fetchmailrc'' run control file. The pathname argument must be either '' __-i __ (Keyword: idfile) Specify an alternate name for the .fetchids file used to save POP3 UIDs. __-n, --norewrite__ (Keyword: no rewrite) Normally, ''fetchmail'' edits RFC-822 address headers (To, From, Cc, Bcc, and Reply-To) in fetched mail so that any mail IDs local to the server are expanded to full addresses (@ and the mailserver hostname are appended). This enables replies on the client to get addressed correctly (otherwise your mailer might think they should be addressed to local users on the client machine!). This option disables the rewrite. (This option is provided to pacify people who are paranoid about having an MTA edit mail headers and want to know they can prevent it, but it is generally not a good idea to actually turn off rewrite.) When using ETRN or ODMR, the rewrite option is ineffective. __-E __ (Keyword: envelope) This option changes the header ''fetchmail'' assumes will carry a copy of the mail's envelope address. Normally this is `X-Envelope-To' but as this header is not standard, practice varies. See the discussion of multidrop address handling below. As a special case, `envelope ''.fetchmailrc'' file. __-Q __ (Keyword: qvirtual) The string prefix assigned to this option will be removed from the user name found in the header specified with the ''envelope'' option (''before'' doing multidrop name mapping or localdomain checking, if either is applicable). This option is useful if you are using ''fetchmail'' to collect the mail for an entire domain and your ISP (or your mail redirection provider) is using qmail. One of the basic features of qmail is the `Delivered-To:' message header. Whenever qmail delivers a message to a local mailbox it puts the username and hostname of the envelope recipient on this line. The major reason for this is to prevent mail loops. To set up qmail to batch mail for a disconnected site the ISP-mailhost will have normally put that site in its `Virtualhosts' control file so it will add a prefix to all mail addresses for this site. This results in mail sent to 'username@userhost.userdom.dom.com' having a `Delivered-To:' line of the form: Delivered-To: mbox-userstr-username@userhost.userdom.dom.com The ISP can make the 'mbox-userstr-' prefix anything they choose but a string matching the user host name is likely. By using the option `envelope Delivered-To:' you can make fetchmail reliably identify the original envelope recipient, but you have to strip the `mbox-userstr-' prefix to deliver to the correct user. This is what this option is for. __--configdump__ Parse the ''~/.fetchmailrc'' file, interpret any command-line options specified, and dump a configuration report to standard output. The configuration report is a data structure assignment in the language Python. This option is meant to be used with an interactive ''~/.fetchmailrc'' editor like ''fetchmailconf'', written in Python. !!USER AUTHENTICATION AND ENCRYPTION All modes except ETRN require authentication of the client to the server. Normal user authentication in ''fetchmail'' is very much like the authentication mechanism of ftp(1). The correct user-id and password depend upon the underlying security system at the mailserver. If the mailserver is a Unix machine on which you have an ordinary user account, your regular login name and password are used with ''fetchmail.'' If you use the same login name on both the server and the client machines, you needn't worry about specifying a user-id with the __-u__ option -- the default behavior is to use your login name on the client machine as the user-id on the server machine. If you use a different login name on the server machine, specify that login name with the __-u__ option. e.g. if your login name is 'jsmith' on a machine named 'mailgrunt', you would start ''fetchmail'' as follows: fetchmail -u jsmith mailgrunt The default behavior of ''fetchmail'' is to prompt you for your mailserver password before the connection is established. This is the safest way to use ''fetchmail'' and ensures that your password will not be compromised. You may also specify your password in your ''~/.fetchmailrc'' file. This is convenient when using ''fetchmail'' in daemon mode or with scripts. If you do not specify a password, and ''fetchmail'' cannot extract one from your ''~/.fetchmailrc'' file, it will look for a ''~/.netrc'' file in your home directory before requesting one interactively; if an entry matching the mailserver is found in that file, the password will be used. Fetchmail first looks for a match on poll name; if it finds none, it checks for a match on via name. See the ftp(1) man page for details of the syntax of the ''~/.netrc'' file. (This feature may allow you to avoid duplicating password information in more than one file.) On mailservers that do not provide ordinary user accounts, your user-id and password are usually assigned by the server administrator when you apply for a mailbox on the server. Contact your server administrator if you don't know the correct user-id and password for your mailbox account. Early versions of POP3 (RFC1081, RFC1225) supported a crude form of independent authentication using the ''rhosts'' file on the mailserver side. Under this RPOP variant, a fixed per-user ID equivalent to a password was sent in clear over a link to a reserved port, with the command RPOP rather than PASS to alert the server that it should do special checking. RPOP is supported by ''fetchmail'' (you can specify `protocol RPOP' to have the program send `RPOP' rather than `PASS') but its use is strongly discouraged. This facility was vulnerable to spoofing and was withdrawn in RFC1460. RFC1460 introduced APOP authentication. In this variant of POP3, you register an APOP password on your server host (the program to do this with on the server is probably called popauth(8)). You put the same password in your ''~/.fetchmailrc'' file. Each time ''fetchmail'' logs in, it sends a cryptographically secure hash of your password and the server greeting time to the server, which can verify it by checking its authorization database. If your ''fetchmail'' was built with Kerberos support and you specify Kerberos authentication (either with --auth or the ''.fetchmailrc'' option __authenticate kerberos_v4__) it will try to get a Kerberos ticket from the mailserver at the start of each query. Note: if either the pollnane or via name is `hesiod', fetchmail will try to use Hesiod to look up the mailserver. If you use POP3 or IMAP with GSSAPI authentication, ''fetchmail'' will expect the server to have RFC1731- or RFC1734-conformant GSSAPI capability, and will use it. Currently this has only been tested over Kerberos V, so you're expected to already have a ticket-granting ticket. You may pass a username different from your principal name using the standard __--user__ command or by the ''.fetchmailrc'' option __user__. If your IMAP daemon returns the PREAUTH response in its greeting line, fetchmail will notice this and skip the normal authentication step. This can be useful, e.g. if you start imapd explicitly using ssh. In this case you can declare the authentication value `ssh' on that site entry to stop ''.fetchmail'' from asking you for a password when it starts up. If you are using POP3, and the server issues a one-time-password challenge conforming to RFC1938, ''fetchmail'' will use your password as a pass phrase to generate the required response. This avoids sending secrets over the net unencrypted. Compuserve's RPA authentication (similar to APOP) is supported. If you compile in the support, ''fetchmail'' will try to perform an RPA pass-phrase authentication instead of sending over the password en clair if it detects '' If you are using IMAP, Microsoft's NTLM authentication (used by Microsoft Exchange) is supported. If you compile in the support, ''fetchmail'' will try to perform an NTLM authentication (instead of sending over the password en clair) whenever the server returns AUTH=NTLM in its capability response. Specify a user option value that looks like `user@domain': the part to the left of the @ will be passed as the username and the part to the right as the NTLM domain. If you are using IPsec, the -T (--netsec) option can be used to pass an IP security request to be used when outgoing IP connections are initialized. You can also do this using the `netsec' server option in the .fetchmailrc file. In either case, the option value is a string in the format accepted by the net_security_strtorequest() function of the inet6_apps library. You can access SSL encrypted services by specifying the --ssl option. You can also do this using the When connecting to an SSL encrypted server, the server presents a certificate to the client for validation. The certificate is checked to verify that the common name in the certificate matches the name of the server being contacted and that the effective and expiration dates in the certificate indicate that it is currently valid. If any of these checks fail, a warning message is printed, but the connection continues. The server certificate does not need to be signed by any specific Certifying Authority and may be a Some SSL encrypted servers may request a client side certificate. A client side public SSL certificate and private SSL key may be specified. If requested by the server, the client certificate is sent to the server for validation. Some servers may require a valid client certificate and may refuse connections if a certificate is not provided or if the certificate is not valid. Some servers may require client side certificates be signed by a recognized Certifying Authority. The format for the key files and the certificate files is that required by the underlying SSL libraries (OpenSSL in the general case). A word of care about the use of SSL: While above mentioned setup with self-signed server certificates retrieved over the wires can protect you from a passive eavesdropper it doesn't help against an active attacker. It's clearly an improvement over sending the passwords in clear but you should be aware that a man-in-the-middle attack is trivially possible (in particular with tools such as dsniff, http://www.monkey.org/~dugsong/dsniff/). Use of an ssh tunnel (see below for some examples) is preferable if you care seriously about the security of your mailbox. __fetchmail__ also supports authentication to the ESMTP server on the client side according to RFC 2554. You can specify a name/password pair to be used with the keywords `esmtpname' and `esmtppassword'; the former defaults to the username of the calling user. !!DAEMON MODE The __--daemon __ or __-d __ option runs ''fetchmail'' in daemon mode. You must specify a numeric argument which is a polling interval in seconds. In daemon mode, ''fetchmail'' puts itself in background and runs forever, querying each specified host and then sleeping for the given polling interval. Simply invoking fetchmail -d 900 will, therefore, poll all the hosts described in your ''~/.fetchmailrc'' file (except those explicitly excluded with the `skip' verb) once every fifteen minutes. It is possible to set a polling interval in your ''~/.fetchmailrc'' file by saying `set daemon '' Only one daemon process is permitted per user; in daemon mode, ''fetchmail'' makes a per-user lockfile to guarantee this. Normally, calling fetchmail with a daemon in the background sends a wakeup signal to the daemon, forcing it to poll mailservers immediately. (The wakeup signal is SIGHUP if fetchmail is running as root, SIGUSR1 otherwise.) The wakeup action also clears any `wedged' flags indicating that connections have wedged due to failed authentication or multiple timeouts. The option __--quit__ will kill a running daemon process instead of waking it up (if there is no such process, ''fetchmail'' notifies you). If the --quit option is the only command-line option, that's all there is to it. The quit option may also be mixed with other command-line options; its effect is to kill any running daemon before doing what the other options specify in combination with the rc file. The __-L __ or __--logfile __ option (keyword: set logfile) allows you to redirect status messages emitted while detached into a specified logfile (follow the option with the logfile name). The logfile is opened for append, so previous messages aren't deleted. This is primarily useful for debugging configurations. The __--syslog__ option (keyword: set syslog) allows you to redirect status and error messages emitted to the syslog(3) system daemon if available. Messages are logged with an id of __fetchmail__, the facility __LOG_MAIL__, and priorities __LOG_ERR__, __LOG_ALERT__ or __LOG_INFO__. This option is intended for logging status and error messages which indicate the status of the daemon and the results while fetching mail from the server(s). Error messages for command line options and parsing the ''.fetchmailrc'' file are still written to stderr, or to the specified log file. The __--nosyslog__ option turns off use of syslog(3), assuming it's turned on in the ''~/.fetchmailrc'' file, or that the __-L__ or __--logfile __ option was used. The __-N__ or --nodetach option suppresses backgrounding and detachment of the daemon process from its control terminal. This is primarily useful for debugging. Note that this also causes the logfile option to be ignored (though perhaps it shouldn't). Note that while running in daemon mode polling a POP2 or IMAP2bis server, transient errors (such as DNS failures or sendmail delivery refusals) may force the fetchall option on for the duration of the next polling cycle. This is a robustness feature. It means that if a message is fetched (and thus marked seen by the mailserver) but not delivered locally due to some transient error, it will be re-fetched during the next poll cycle. (The IMAP logic doesn't delete messages until they're delivered, so this problem does not arise.) If you touch or change the ''~/.fetchmailrc'' file while fetchmail is running in daemon mode, this will be detected at the beginning of the next poll cycle. When a changed ''~/.fetchmailrc'' is detected, fetchmail rereads it and restarts from scratch (using exec(2); no state information is retained in the new instance). Note also that if you break the ''~/.fetchmailrc'' file's syntax, the new instance will softly and silently vanish away on startup. !!ADMINISTRATIVE OPTIONS The __--postmaster __ option (keyword: set postmaster) specifies the last-resort username to which multidrop mail is to be forwarded if no matching local recipient can be found. Normally this is just the user who invoked fetchmail. If the invoking user is root, then the default of this option is the user `postmaster'. Setting postmaster to the empty string causes such mail to be discarded. The __--nobounce__ option suppresses the normal action of bouncing errors back to the sender in an RFC1894-conformant error message. If nobounce is on, the message will go to the postmaster instead. The __--invisible__ option (keyword: set invisible) tries to make fetchmail invisible. Normally, fetchmail behaves like any other MTA would -- it generates a Received header into each message describing its place in the chain of transmission, and tells the MTA it forwards to that the mail came from the machine fetchmail itself is running on. If the invisible option is on, the Received header is suppressed and fetchmail tries to spoof the MTA it forwards to into thinking it came directly from the mailserver host. The __--showdots__ option (keyword: set showdots) forces fetchmail to show progress dots even if the current tty is not stdout (for example logfiles). Starting with fetchmail version 5.3.0, progress dots are only shown on stdout by default. By specifying the __--tracepolls__ option, you can ask fetchmail to add information to the Received header on the form __.fetchmailrc'', this is called `tracepolls'. !!RETRIEVAL FAILURE MODES The protocols ''fetchmail'' uses to talk to mailservers are next to bulletproof. In normal operation forwarding to port 25, no message is ever deleted (or even marked for deletion) on the host until the SMTP listener on the client side has acknowledged to ''fetchmail'' that the message has been either accepted for delivery or rejected due to a spam block. When forwarding to an MDA, however, there is more possibility of error. Some MDAs are `safe' and reliably return a nonzero status on any delivery error, even one due to temporary resource limits. The well-known procmail(1) program is like this; so are most programs designed as mail transport agents, such as sendmail(1), and exim(1). These programs give back a reliable positive acknowledgement and can be used with the mda option with no risk of mail loss. Unsafe MDAs, though, may return 0 even on delivery failure. If this happens, you will lose mail. The normal mode of ''fetchmail'' is to try to download only `new' messages, leaving untouched (and undeleted) messages you have already read directly on the server (or fetched with a previous ''fetchmail --keep''). But you may find that messages you've already read on the server are being fetched (and deleted) even when you don't specify --all. There are several reasons this can happen. One could be that you're using POP2. The POP2 protocol includes no representation of `new' or `old' state in messages, so ''fetchmail'' must treat all messages as new all the time. But POP2 is obsolete, so this is unlikely. Under POP3, blame RFC1725. That version of the POP3 protocol specification removed the LAST command, and some POP servers follow it (you can verify this by invoking ''fetchmail -v'' to the mailserver and watching the response to LAST early in the query). The ''fetchmail'' code tries to compensate by using POP3's UID feature, storing the identifiers of messages seen in each session until the next session, in the ''.fetchids'' file. But this doesn't track messages seen with other clients, or read directly with a mailer on the host but not deleted afterward. A better solution would be to switch to IMAP. Another potential POP3 problem might be servers that insert messages in the middle of mailboxes (some VMS implementations of mail are rumored to do this). The ''fetchmail'' code assumes that new messages are appended to the end of the mailbox; when this is not true it may treat some old messages as new and vice versa. The only real fix for this problem is to switch to IMAP. Yet another POP3 problem is that if they can't make tempfiles in the user's home directory, some POP3 servers will hand back an undocumented response that causes fetchmail to spuriously report The IMAP code uses the presence or absence of the server flag Seen to decide whether or not a message is new. Under Unix, it counts on your IMAP server to notice the BSD-style Status flags set by mail user agents and set the Seen flag from them when appropriate. All Unix IMAP servers we know of do this, though it's not specified by the IMAP RFCs. If you ever trip over a server that doesn't, the symptom will be that messages you have already read on your host will look new to the server. In this (unlikely) case, only messages you fetched with ''fetchmail --keep'' will be both undeleted and marked old. In ETRN and ODMR modes, ''fetchmail'' does not actually retrieve messages; instead, it asks the server's SMTP listener to start a queue flush to the client via SMTP. Therefore it sends only undelivered messages. !!SPAM FILTERING Many SMTP listeners allow administrators to set up `spam filters' that block unsolicited email from specified domains. A MAIL FROM or DATA line that triggers this feature will elicit an SMTP response which (unfortunately) varies according to the listener. Newer versions of ''sendmail'' return an error code of 571. This return value is blessed by RFC1893 as '' According to current drafts of the replacement for RFC821, the correct thing to return in this situation is 550 The ''exim'' MTA returns 501 '' The ''postfix'' MTA runs 554 as an antispam response. The ''fetchmail'' code recognizes and discards the message on any of a list of responses that defaults to [[571, 550, 501, 554] but can be set with the `antispam' option. This is one of the ''only'' three circumstance under which fetchmail ever discards mail (the others are the 552 and 553 errors described below, and the suppression of multidropped messages with a message-ID already seen). If ''fetchmail'' is fetching from an IMAP server, the antispam response will be detected and the message rejected immediately after the headers have been fetched, without reading the message body. Thus, you won't pay for downloading spam message bodies. If the ''spambounce'' option is on, mail that is spam-blocked triggers an RFC1892 bounce message informing the originator that we do not accept mail from it. !!SMTP/ESMTP ERROR HANDLING Besides the spam-blocking described above, fetchmail takes special actions on the following SMTP/ESMTP error responses 452 (insufficient system storage) Leave the message in the server mailbox for later retrieval. 552 (message exceeds fixed maximum message size) Delete the message from the server. Send bounce-mail to the originator. 553 (invalid sending domain) Delete the message from the server. Don't even try to send bounce-mail to the originator. Other errors trigger bounce mail back to the originator. !!THE RUN CONTROL FILE The preferred way to set up fetchmail is to write a ''.fetchmailrc'' file in your home directory (you may do this directly, with a text editor, or indirectly via ''fetchmailconf''). When there is a conflict between the command-line arguments and the arguments in this file, the command-line arguments take precedence. To protect the security of your passwords, when --version is not on your ''~/.fetchmailrc'' may not have more than 0600 (u=rw,g=,o=) permissions; ''fetchmail'' will complain and exit otherwise. You may read the ''.fetchmailrc'' file as a list of commands to be executed when ''fetchmail'' is called with no arguments. __Run Control Syntax__ Comments begin with a '#' and extend through the end of the line. Otherwise the file consists of a series of server entries or global option statements in a free-format, token-oriented syntax. There are four kinds of tokens: grammar keywords, numbers (i.e. decimal digit sequences), unquoted strings, and quoted strings. A quoted string is bounded by double quotes and may contain whitespace (and quoted digits are treated as a string). An unquoted string is any whitespace-delimited token that is neither numeric, string quoted nor contains the special characters `,', `;', `:', or `='. Any amount of whitespace separates tokens in server entries, but is otherwise ignored. You may use standard C-style escapes (n, t, b, octal, and hex) to embed non-printable characters or string delimiters in strings. Each server entry consists of one of the keywords `poll' or `skip', followed by a server name, followed by server options, followed by any number of user descriptions. Note: the most common cause of syntax errors is mixing up user and server options. For backward compatibility, the word `server' is a synonym for `poll'. You can use the noise keywords `and', `with', `has', `wants', and `options' anywhere in an entry to make it resemble English. They're ignored, but but can make entries much easier to read at a glance. The punctuation characters ':', ';' and ',' are also ignored. __Poll vs. Skip__ The `poll' verb tells fetchmail to query this host when it is run with no arguments. The `skip' verb tells ''fetchmail'' not to poll this host unless it is explicitly named on the command line. (The `skip' verb allows you to experiment with test entries safely, or easily disable entries for hosts that are temporarily down.) __Keyword/Option Summary__ Here are the legal options. Keyword suffixes enclosed in square brackets are optional. Those corresponding to command-line options are followed by `-' and the appropriate option letter. Here are the legal global options: Here are the legal server options: Here are the legal user options: Remember that all user options must ''follow'' all server options. In the .fetchmailrc file, the `envelope' string argument may be preceded by a whitespace-separated number. This number, if specified, is the number of such headers to skip (that is, an argument of 1 selects the second header of the given type). This is sometime useful for ignoring bogus Received headers created by an ISP's local delivery agent. __Keywords Not Corresponding To Option Switches__ The `folder' and `smtphost' options (unlike their command-line equivalents) can take a space- or comma-separated list of names following them. All options correspond to the obvious command-line arguments, except the following: `via', `interval', `aka', `is', `to', `dns'/`no dns', `checkalias'/`no checkalias', `password', `preconnect', `postconnect', `localdomains', `stripcr'/`no stripcr', `forcecr'/`no forcecr', `pass8bits'/`no pass8bits' `dropstatus/no dropstatus', `dropdelivered/no dropdelivered', `mimedecode/no mimedecode', `idle/no idle', and `no envelope'. The `via' option is for if you want to have more than one configuration pointing at the same site. If it is present, the string argument will be taken as the actual DNS name of the mailserver host to query. This will override the argument of poll, which can then simply be a distinct label for the configuration (e.g. what you would give on the command line to explicitly query this host). The `interval' option (which takes a numeric argument) allows you to poll a server less frequently than the basic poll interval. If you say `interval N' the server this option is attached to will only be queried every N poll intervals. The `is' or `to' keywords associate the following local (client) name(s) (or server-name to client-name mappings separated by =) with the mailserver user name in the entry. If an is/to list has `*' as its last name, unrecognized names are simply passed through. A single local name can be used to support redirecting your mail when your username on the client machine is different from your name on the mailserver. When there is only a single local name, mail is forwarded to that local username regardless of the message's Received, To, Cc, and Bcc headers. In this case ''fetchmail'' never does DNS lookups. When there is more than one local name (or name mapping) the ''fetchmail'' code does look at the Received, To, Cc, and Bcc headers of retrieved mail (this is `multidrop mode'). It looks for addresses with hostname parts that match your poll name or your `via', `aka' or `localdomains' options, and usually also for hostname parts which DNS tells it are aliases of the mailserver. See the discussion of `dns', `checkalias', `localdomains', and `aka' for details on how matching addresses are handled. If ''fetchmail'' cannot match any mailserver usernames or localdomain addresses, the mail will be bounced. Normally it will be bounced to the sender, but if `nobounce' is on it will go to the postmaster (which in turn defaults to being the calling user). The `dns' option (normally on) controls the way addresses from multidrop mailboxes are checked. On, it enables logic to check each host address that doesn't match an `aka' or `localdomains' declaration by looking it up with DNS. When a mailserver username is recognized attached to a matching hostname part, its local mapping is added to the list of local recipients. The `checkalias' option (normally off) extends the lookups performed by the `dns' keyword in multidrop mode, providing a way to cope with remote MTAs that identify themselves using their canonical name, while they're polled using an alias. When such a server is polled, checks to extract the envelope address fail, and ''fetchmail'' reverts to delivery using the To/Cc/Bcc headers (See below `Header vs. Envelope addresses'). Specifying this option instructs ''fetchmail'' to retrieve all the IP addresses associated with both the poll name and the name used by the remote MTA and to do a comparison of the IP addresses. This comes in handy in situations where the remote server undergoes frequent canonical name changes, that would otherwise require modifications to the rcfile. `checkalias' has no effect if `no dns' is specified in the rcfile. The `aka' option is for use with multidrop mailboxes. It allows you to pre-declare a list of DNS aliases for a server. This is an optimization hack that allows you to trade space for speed. When ''fetchmail'', while processing a multidrop mailbox, grovels through message headers looking for names of the mailserver, pre-declaring common ones can save it from having to do DNS lookups. Note: the names you give as arguments to `aka' are matched as suffixes -- if you specify (say) `aka netaxs.com', this will match not just a hostnamed netaxs.com, but any hostname that ends with `.netaxs.com'; such as (say) pop3.netaxs.com and mail.netaxs.com. The `localdomains' option allows you to declare a list of domains which fetchmail should consider local. When fetchmail is parsing address lines in multidrop modes, and a trailing segment of a host name matches a declared local domain, that address is passed through to the listener or MDA unaltered (local-name mappings are ''not'' applied). If you are using `localdomains', you may also need to specify `no envelope', which disables ''fetchmail'''s normal attempt to deduce an envelope address from the Received line or X-Envelope-To header or whatever header has been previously set by `envelope'. If you set `no envelope' in the defaults entry it is possible to undo that in individual entries by using `envelope '' The __password__ option requires a string argument, which is the password to be used with the entry's server. The `preconnect' keyword allows you to specify a shell command to be executed just before each time ''fetchmail'' establishes a mailserver connection. This may be useful if you are attempting to set up secure POP connections with the aid of ssh(1). If the command returns a nonzero status, the poll of that mailserver will be aborted. Similarly, the `postconnect' keyword similarly allows you to specify a shell command to be executed just after each time a mailserver connection is taken down. The `forcecr' option controls whether lines terminated by LF only are given CRLF termination before forwarding. Strictly speaking RFC821 requires this, but few MTAs enforce the requirement it so this option is normally off (only one such MTA, qmail, is in significant use at time of writing). The `stripcr' option controls whether carriage returns are stripped out of retrieved mail before it is forwarded. It is normally not necessary to set this, because it defaults to `on' (CR stripping enabled) when there is an MDA declared but `off' (CR stripping disabled) when forwarding is via SMTP. If `stripcr' and `forcecr' are both on, `stripcr' will override. The `pass8bits' option exists to cope with Microsoft mail programs that stupidly slap a fetchmail'' declares BODY=7BIT to an ESMTP-capable listener; this causes problems for messages actually using 8-bit ISO or KOI-8 character sets, which will be garbled by having the high bits of all characters stripped. If `pass8bits' is on, ''fetchmail'' is forced to declare BODY=8BITMIME to any ESMTP-capable listener. If the listener is 8-bit-clean (as all the major ones now are) the right thing will probably result. The `dropstatus' option controls whether nonempty Status and X-Mozilla-Status lines are retained in fetched mail (the default) or discarded. Retaining them allows your MUA to see what messages (if any) were marked seen on the server. On the other hand, it can confuse some new-mail notifiers, which assume that anything with a Status line in it has been seen. (Note: the empty Status lines inserted by some buggy POP servers are unconditionally discarded.) The `dropdelivered' option controls wether Delivered-To headers will be kept in fetched mail (the default) or discarded. These headers are added by Qmail and Postfix mailservers in order to avoid mail loops but may get in your way if you try to The `mimedecode' option controls whether MIME messages using the quoted-printable encoding are automatically converted into pure 8-bit data. If you are delivering mail to an ESMTP-capable, 8-bit-clean listener (that includes all of the major MTAs like sendmail), then this will automatically convert quoted-printable message headers and data into 8-bit data, making it easier to understand when reading mail. If your e-mail programs know how to deal with MIME messages, then this option is not needed. The mimedecode option is off by default, because doing RFC2047 conversion on headers throws away character-set information and can lead to bad results if the encoding of the headers differs from the body encoding. The `idle' option is usable only with IMAP servers supporting the RFC2177 IDLE command extension. If it is enabled, and fetchmail detects that IDLE is supported, an IDLE will be issued at the end of each poll. This will tell the IMAP server to hold the connection open and notify the client when new mail is available. If you need to poll a link frequently, IDLE can save bandwidth by eliminating TCP/IP connects and LOGIN/LOGOUT sequences. On the other hand, an IDLE connection will eat almost all of your fetchmail's time, because it will never drop the connection and allow other pools to occur unless the server times out the IDLE. It also doesn't work with multiple folders; only the first folder will ever be polled. The `properties' option is an extension mechanism. It takes a string argument, which is ignored by fetchmail itself. The string argument may be used to store configuration information for scripts which require it. In particular, the output of `--configdump' option will make properties associated with a user entry readily available to a Python script. __Miscellaneous Run Control Options__ The words `here' and `there' have useful English-like significance. Normally `user eric is esr' would mean that mail for the remote user `eric' is to be delivered to `esr', but you can make this clearer by saying `user eric there is esr here', or reverse it by saying `user esr here is eric there' Legal protocol identifiers for use with the `protocol' keyword are: auto (or AUTO) pop2 (or POP2) pop3 (or POP3) sdps (or SDPS) imap (or IMAP) apop (or APOP) kpop (or KPOP) Legal authentication types are `any', `password', `kerberos', 'kereberos_v5' and `gssapi', `cram-md5', `otp', `ntlm', `ssh`. The `password' type specifies authentication by normal transmission of a password (the password may be plaintext or subject to protocol-specific encryption as in APOP); `kerberos' tells ''fetchmail'' to try to get a Kerberos ticket at the start of each query instead, and send an arbitrary string as the password; and `gssapi' tells fetchmail to use GSSAPI authentication. See the description of the `auth' keyword for more. Specifying `kpop' sets POP3 protocol over port 1109 with Kerberos V4 authentication. These defaults may be overridden by later options. There are currently four global option statements; `set logfile' followed by a string sets the same global specified by --logfile. A command-line --logfile option will override this. Also, `set daemon' sets the poll interval as --daemon does. This can be overridden by a command-line --daemon option; in particular --daemon 0 can be used to force foreground operation. The `set postmaster' statement sets the address to which multidrop mail defaults if there are no local matches. Finally, `set syslog' sends log messages to syslogd(8). !!INTERACTION WITH RFC 822 When trying to determine the originating address of a message, fetchmail looks through headers in the following order: Return-Path: Resent-Sender: (ignored if it doesn't contain an @ or !) Sender: (ignored if it doesn't contain an @ or !) Resent-From: From: Reply-To: Apparently-From: The originating address is used for logging, and to set the MAIL FROM address when forwarding to SMTP. This order is intended to cope gracefully with receiving mailing list messages in multidrop mode. The intent is that if a local address doesn't exist, the bounce message won't be returned blindly to the author or to the list itself, but rather to the list manager (which is less annoying). In multidrop mode, destination headers are processed as follows: First, fetchmail looks for the Received: header (or whichever one is specified by the `envelope' option) to determine the local recipient address. If the mail is addressed to more than one recipient, the Received line won't contain any information regarding recipient addresses. Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc: lines. If they exists, they should contain the final recipients and have precedence over their To:/Cc:/Bcc: counterparts. If the Resent-* lines doesn't exist, the To:, Cc:, Bcc: and Apparently-To: lines are looked for. (The presence of a Resent-To: is taken to imply that the person referred by the To: address has already received the original copy of the mail). !!CONFIGURATION EXAMPLES Note that although there are password declarations in a good many of the examples below, this is mainly for illustrative purposes. We recommend stashing account/password pairs in your $HOME/.netrc file, where they can be used not just by fetchmail but by ftp(1) and other programs. Basic format is: poll SERVERNAME protocol PROTOCOL username NAME password PASSWORD Example: poll pop.provider.net protocol pop3 username Or, using some abbreviations: poll pop.provider.net proto pop3 user Multiple servers may be listed: poll pop.provider.net proto pop3 user Here's a version of those two with more whitespace and some noise words: poll pop.provider.net proto pop3 user This version is much easier to read and doesn't cost significantly more (parsing is done only once, at startup time). If you need to include whitespace in a parameter string, enclose the string in double quotes. Thus: poll mail.provider.net with proto pop3: user You may have an initial server description headed by the keyword `defaults' instead of `poll' followed by a name. Such a record is interpreted as defaults for all queries to use. It may be overwritten by individual server descriptions. So, you could write: defaults proto pop3 user It's possible to specify more than one user per server (this is only likely to be useful when running fetchmail in daemon mode as root). The `user' keyword leads off a user description, and every user specification in a multi-user entry must include it. Here's an example: poll pop.provider.net proto pop3 port 3111 user This associates the local username `smith' with the pop.provider.net username `jsmith' and the local username `jjones' with the pop.provider.net username `jones'. Mail for `jones' is kept on the server after download. Here's what a simple retrieval configuration for a multi-drop mailbox looks like: poll pop.provider.net: user maildrop with pass secret1 to golux 'hurkle'='happy' snark here This says that the mailbox of account `maildrop' on the server is a multi-drop box, and that messages in it should be parsed for the server user names `golux', `hurkle', and `snark'. It further specifies that `golux' and `snark' have the same name on the client as on the server, but mail for server user `hurkle' should be delivered to client user `happy'. Here's an example of another kind of multidrop connection: poll pop.provider.net localdomains loonytoons.org toons.org: user maildrop with pass secret1 to * here This also says that the mailbox of account `maildrop' on the server is a multi-drop box. It tells fetchmail that any address in the loonytoons.org or toons.org domains (including subdomain addresses like `joe@daffy.loonytoons.org') should be passed through to the local SMTP listener without modification. Be careful of mail loops if you do this! Here's an example configuration using ssh and the plugin option. The queries are made directly on the stdin and stdout of imapd via ssh. Note that in this setup, IMAP authentication can be skipped. poll mailhost.net with proto imap: plugin !!THE USE AND ABUSE OF MULTIDROP MAILBOXES Use the multiple-local-recipients feature with caution -- it can bite. All multidrop features are ineffective in ETRN and ODMR modes. Also, note that in multidrop mode duplicate mails are suppressed. A piece of mail is considered duplicate if it has the same message-ID as the message immediately preceding and more than one addressee. Such runs of messages may be generated when copies of a message addressed to multiple users are delivered to a multidrop box. __Header vs. Envelope addresses__ The fundamental problem is that by having your mailserver toss several peoples' mail in a single maildrop box, you may have thrown away potentially vital information about who each piece of mail was actually addressed to (the `envelope address', as opposed to the header addresses in the RFC822 To/Cc/Bcc headers). This `envelope address' is the address you need in order to reroute mail properly. Sometimes ''fetchmail'' can deduce the envelope address. If the mailserver MTA is ''sendmail'' and the item of mail had just one recipient, the MTA will have written a `by/for' clause that gives the envelope addressee into its Received header. But this doesn't work reliably for other MTAs, nor if there is more than one recipient. By default, ''fetchmail'' looks for envelope addresses in these lines; you can restore this default with -E '' Alternatively, some SMTP listeners and/or mail servers insert a header in each message containing a copy of the envelope addresses. This header (when it exists) is often `X-Envelope-To'. Fetchmail's assumption about this can be changed with the -E or `envelope' option. Note that writing an envelope header of this kind exposes the names of recipients (including blind-copy recipients) to all receivers of the messages; it is therefore regarded by some administrators as a security/privacy problem. A slight variation of the `X-Envelope-To' header is the `Delivered-To' put by qmail to avoid mail loops. It will probably prefix the user name with a string that normally matches the user's domain. To remove this prefix you can use the -Q or `qvirtual' option. Sometimes, unfortunately, neither of these methods works. When they all fail, fetchmail must fall back on the contents of To/Cc/Bcc headers to try to determine recipient addressees -- and these are not reliable. In particular, mailing-list software often ships mail with only the list broadcast address in the To header. When ''fetchmail'' cannot deduce a recipient address that is local, and the intended recipient address was anyone other than fetchmail's invoking user, mail will get lost. This is what makes the multidrop feature risky. A related problem is that when you blind-copy a mail message, the Bcc information is carried ''only'' as envelope address (it's not put in the headers fetchmail can see unless there is an X-Envelope header). Thus, blind-copying to someone who gets mail over a fetchmail link will fail unless the the mailserver host routinely writes X-Envelope or an equivalent header into messages in your maildrop. __Good Ways To Use Multidrop Mailboxes__ Multiple local names can be used to administer a mailing list from the client side of a ''fetchmail'' collection. Suppose your name is `esr', and you want to both pick up your own mail and maintain a mailing list called (say) '' On your server, you can alias `fetchmail-friends' to `esr'; then, in your ''.fetchmailrc'', declare `to esr fetchmail-friends here'. Then, when mail including `fetchmail-friends' as a local address gets fetched, the list name will be appended to the list of recipients your SMTP listener sees. Therefore it will undergo alias expansion locally. Be sure to include `esr' in the local alias expansion of fetchmail-friends, or you'll never see mail sent only to the list. Also be sure that your listener has the '' This trick is not without its problems, however. You'll begin to see this when a message comes in that is addressed only to a mailing list you do ''not'' have declared as a local name. Each such message will feature an `X-Fetchmail-Warning' header which is generated because fetchmail cannot find a valid local name in the recipient addresses. Such messages default (as was described above) to being sent to the local user running ''fetchmail'', but the program has no way to know that that's actually the right thing. __Bad Ways To Abuse Multidrop Mailboxes__ Multidrop mailboxes and ''fetchmail'' serving multiple users in daemon mode do not mix. The problem, again, is mail from mailing lists, which typically does not have an individual recipient address on it. Unless ''fetchmail'' can deduce an envelope address, such mail will only go to the account running fetchmail (probably root). Also, blind-copied users are very likely never to see their mail at all. If you're tempted to use ''fetchmail'' to retrieve mail for multiple users from a single mail drop via POP or IMAP, think again (and reread the section on header and envelope addresses above). It would be smarter to just let the mail sit in the mailserver's queue and use fetchmail's ETRN or ODMR modes to trigger SMTP sends periodically (of course, this means you have to poll more frequently than the mailserver's expiry period). If you can't arrange this, try setting up a UUCP feed. If you absolutely ''must'' use multidrop for this purpose, make sure your mailserver writes an envelope-address header that fetchmail can see. Otherwise you ''will'' lose mail and it ''will'' come back to haunt you. __Speeding Up Multidrop Checking__ Normally, when multiple users are declared ''fetchmail'' extracts recipient addresses as described above and checks each host part with DNS to see if it's an alias of the mailserver. If so, the name mappings described in the to ... here declaration are done and the mail locally delivered. This is the safest but also slowest method. To speed it up, pre-declare mailserver aliases with `aka'; these are checked before DNS lookups are done. If you're certain your aka list contains __all__ DNS aliases of the mailserver (and all MX names pointing at it) you can declare `no dns' to suppress DNS lookups entirely and ''only'' match against the aka list. !!EXIT CODES To facilitate the use of ''fetchmail'' in shell scripts, an exit code is returned to give an indication of what occurred during a given connection. The exit codes returned by ''fetchmail'' are as follows: 0 One or more messages were successfully retrieved (or, if the -c option was selected, were found waiting but not retrieved). 1 There was no mail awaiting retrieval. (There may have been old mail still on the server but not selected for retrieval.) 2 An error was encountered when attempting to open a socket to retrieve mail. If you don't know what a socket is, don't worry about it -- just treat this as an 'unrecoverable error'. This error can also be because a protocol fetchmail wants to use is not listed in /etc/services. 3 The user authentication step failed. This usually means that a bad user-id, password, or APOP id was specified. Or it may mean that you tried to run fetchmail under circumstances where it did not have standard input attached to a terminal and could not prompt for a missing password. 4 Some sort of fatal protocol error was detected. 5 There was a syntax error in the arguments to ''fetchmail.'' 6 The run control file had bad permissions. 7 There was an error condition reported by the server. Can also fire if ''fetchmail'' timed out while waiting for the server. 8 Client-side exclusion error. This means ''fetchmail'' either found another copy of itself already running, or failed in such a way that it isn't sure whether another copy is running. 9 The user authentication step failed because the server responded 10 The ''fetchmail'' run failed while trying to do an SMTP port open or transaction. 11 Fatal DNS error. Fetchmail encountered an error while performing a DNS lookup at startup and could not proceed. 12 BSMTP batch file could not be opened. 13 Poll terminated by a fetch limit (see the --fetchlimit option). 14 Server busy indication. 23 Internal error. You should see a message on standard error with details. When ''fetchmail'' queries more than one host, return status is 0 if ''any'' query successfully retrieved mail. Otherwise the returned error status is that of the last host queried. !!FILES ~/.fetchmailrc default run control file ~/.fetchids default location of file associating hosts with last message IDs seen (used only with newer RFC1725-compliant POP3 servers supporting the UIDL command). ~/.fetchmail.pid lock file to help prevent concurrent runs (non-root mode). ~/.netrc your FTP run control file, which (if present) will be searched for passwords as a last resort before prompting for one interactively. /var/run/fetchmail.pid lock file to help prevent concurrent runs (root mode, Linux systems). /etc/fetchmail.pid lock file to help prevent concurrent runs (root mode, systems without /var/run). !!ENVIRONMENT If the FETCHMAILUSER variable is set, it is used as the name of the calling user (default local name) for purposes such as mailing error notifications. Otherwise, if either the LOGNAME or USER variable is correctly set (e.g. the corresponding UID matches the session user ID) then that name is used as the default local name. Otherwise getpwuid(3) must be able to retrieve a password entry for the session ID (this elaborate logic is designed to handle the case of multiple names per userid gracefully). If the environment variable FETCHMAILHOME is set to a valid and existing directory name, the .fetchmailrc and .fetchids and .fetchmail.pid files are put there instead of in the invoking user's home directory (and lose the leading dots on theirt names). The .netrc file is looked for in the the invoking user's home directory regardless of FETCHMAILHOME's setting. !!SIGNALS If a ''fetchmail'' daemon is running as root, SIGHUP wakes it up from its sleep phase and forces a poll of all non-skipped servers (this is in accordance with the usual conventions for system daemons). If ''fetchmail'' is running in daemon mode as non-root, use SIGUSR1 to wake it (this is so SIGHUP due to logout can retain the default action of killing it). Running ''fetchmail'' in foreground while a background fetchmail is running will do whichever of these is appropriate to wake it up. !!BUGS AND KNOWN PROBLEMS The mda and plugin options interact badly. In order to collect error status from the MDA, fetchmail has to change its normal signal handling so that dead plugin processes don't get reaped until the end of the poll cycle. This can cause resource starvation if too many zombies accumulate. So either don't deliver to a MDA using plugins or risk being overrun by an army of undead. The RFC822 address parser used in multidrop mode chokes on some @-addresses that are technically legal but bizarre. Strange uses of quoting and embedded comments are likely to confuse it. In a message with multiple envelope headers, only the last one processed will be visible to fetchmail. To get around this, use a mailserver-side filter that consolidates the contents of all envelope headers into a single one (procmail, mailagent, or maildrop can be programmed to do this fairly easily). Use of some of these protocols requires that the program send unencrypted passwords over the TCP/IP connection to the mailserver. This creates a risk that name/password pairs might be snaffled with a packet sniffer or more sophisticated monitoring software. Under Linux and FreeBSD, the --interface option can be used to restrict polling to availability of a specific interface device with a specific local or remote IP address, but snooping is still possible if (a) either host has a network device that can be opened in promiscuous mode, or (b) the intervening network link can be tapped. We recommend the use of ssh(1) tunnelling to not only shroud your passwords but encrypt the entire conversation. Use of the %F or %T escapes in an mda option could open a security hole, because they pass text manipulable by an attacker to a shell command. Potential shell characters are replaced by `_' before execution. The hole is further reduced by the fact that fetchmail temporarily discards any suid privileges it may have while running the MDA. For maximum safety, however, don't use an mda command containing %F or %T when fetchmail is run from the root account itself. Fetchmail's method of sending bouncemail and spam bounces requires that port 25 of localhost be available for sending mail via SMTP. If you modify a ''~/.fetchmailrc'' while a background instance is running and break the syntax, the background instance will die silently. Unfortunately, it can't die noisily because we don't yet know whether syslog should be enabled. The -f - option (reading a configuration from stdin) is incompatible with the plugin option. The UIDL code is generally flaky and tends to lose its state on errors and line drops (so that old messages are re-seen). If this happens to you, switch to IMAP4. The `principal' option only handles Kerberos IV, not V. Send comments, bug reports, gripes, and the like to the fetchmail-friends list !!AUTHOR Eric S. Raymond popclient'', by Carl Harris '' !!SEE ALSO mutt(1), elm(1), mail(1), sendmail(8), popd(8), imapd(8), netrc(5) !!APPLICABLE STANDARDS SMTP/ESMTP: RFC 821, RFC2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC 1985, RFC 2554 mail: RFC 822, RFC2822, RFC 1123, RFC 1892, RFC 1894 POP2: RFC 937 POP3: RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC1734, RFC 1939, RFC 1957, RFC2195, RFC 2449 APOP: RFC 1460, RFC 1725, RFC 1939 RPOP: RFC 1081, RFC 1225 IMAP2/IMAP2BIS: RFC 1176, RFC 1732 IMAP4/IMAP4rev1: RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC 2177, RFC 2683 ETRN: RFC 1985 ODMR/ATRN: RFC 2645 OTP: RFC 1938 LMTP: RFC 2033 GSSAPI: RFC 1508 ----
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